Self-holding electromagnetically driven device

ABSTRACT

An armature secured to an operating rod is located between two permanent magnets so as to be normally held fast to one of these two permanent magnets which are spaced apart and in opposed polarity relationship. Each permanent magnet is provided with an electromagnetic coil wound around it which is adapted, when energized by a pulse of short duration, to produce a magnetic field in the same direction as that of the associated permanent magnet, whereby the armature is driven from a position next to the other permanent magnet to a position adjacent the associated permanent magnet and held onto it by virtue of the magnetic force thereof, without requiring any further application of electric power to maintain the armature in its displaced position.

United States Patent Mikio Komatsu No. 384, Tokiwadai, Hodogaya-ku, Yokohama-shi, Kanagawa-ken, Japan Inventor Appl. No. 23,619

Filed Mar. 30, 1970 Patented Jan. 11,1972

Priority Apr. 3, 1969 Japan 44/25774 SELF-HOLDING ELECTROMAGNETICALLY DRIVEN DEVICE [56] References Cited UNITED STATES PATENTS 3,460,081 8/1969 Tillman 335/234 3,514,674 5/1970 Toshio Ito et al. 317/1555 Primary Examiner-L. T. l-lix Attorney-Karl F. Ross ABSTRACT: An armature secured to an operating rod is located between two permanent magnets so as to be normally held fast to one of these two permanent magnets which are spaced apart and in opposed polarity relationship. Each permanent magnet is provided with an electromagnetic coil wound around it which is adapted, when energized by a pulse of short duration, to produce a magnetic field in the same direction as that of the associated permanent magnet, whereby the armature is driven from a position next to the other permanent magnet to a position adjacent the associated permanent magnet and held onto it by virtue of the magnetic force thereof, without requiring any further application of electric power to maintain the armature in its displaced posi- PATENTED JAN! 1 1972 3534.7 5

This invention relates to a self-holding or bistable electromagnetically driven device used for switching on and off a relay, an electric switch, a valve or the like, and more particularly to a device of this kind wherein an armature secured to an operating rod is driven from a first stable position to a second stable position in response to energization of an electromagnetic coil which is employed to actuate the armature,

' being thereupon held in its second stable or actuated position by means of magnetic force.

DESCRIPTION OF THE PRIOR ART In knownelectromagnetically driven system having an armature secured to a control shaft or an operating rod, the armature is driven to an off-normal position when an electromagnetic coil is energized, and in order to maintain the armature inthis off-normal position it is necessary to apply a constant energizing voltage to the electromagnetic coil. This results in consumption of large electric power and generation of large amount of heat in operation.

Other electromagnetically driven devices are known in which the armature is driven to the shifted position in response to energization of the electromagnetic coil and held magnetically in that position bymeans of residual magnetism retained in .the magnetic circuit of the electromagnetic coil. Systems of this type, however, have the drawback that the magnetic force for maintaining the annature in its alternate position is so weak'that they cannot be used where they would be subjected to vibration or shock, and further in that they are usually complicated in construction and costly to manufacture.

SUMMARY OF THE INVENTION In accordance with this invention, a self-holding electromagnetically driven device is provided which comprises a pair of permanent magnets, preferably in the form of disks, which are spaced. apart and face each other in opposed polarity relationship. Each permanent magnet is provided with a central aperture and has an electromagnetic coil wound around it. An armature, preferably in the form of a disk, is provided between the permanent magnets in aligned relationship therewith. The armature issecured to an operating rod which extends through the central apertures of the permanent magnets. Each electromagnetic coil is adapted, when energized, to produce a magnetic filed in the same direction as that of the associated permanent magnet. The armature has two stable positions, i.e. it is held onto either of the two pennanent magnets by means of magnetic force. With the armature attracted by one permanent magnet, when the electromagnetic coil would around the other permanent magnet is energized by an electric pulse of short duration, the magnetic force produced by the energized coil in cooperation with the magnetic force of the other permanent magnet causes the annature to be pulled toward that other magnet, whereupon the armature is held onto same by virtue of its magnetic force without requiring any further application of electric power to the electromagnetic coil. In this state, when the electromagnetic coil wound around the first permanent magnet is energized by another electric pulse of short duration, a similar operation takes place and the armature is driven from the other permanent magnet to the first one and held fast thereto by means of its magnetic force. Thus, the electromagnetically driven device in accordance with the invention does not require a constant or continuous energization of coils to maintain the armature in the last position into which it is moved, and therefore it can be referred to as a self-holding or bistable device. The device according to the invention can minimize the electric power consumed and the heat generated during operation, and is very simple in construction and reliable in operation.

The other features and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawing in which;

FIG. I shows diagrammatically, partially in vertical section, one embodiment of the self-holding electromagnetically driven device according to the invention together with an'external power source therefor;

FIG. 2 is a top plan view of the device shown in FIG. 1;

FIG. 3 and FIG. 4 are a sectional perspective and a sectional side view of the device, respectively, illustrating how the elements of the device of FIG. I are assembled in a casing in practice; and

FIG. 5 shows a modification of the device in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS For the present purpose, the invention is described as it is utilized in a valve device to control the passage of liquid. However, it should be understood that its use is not limited to this function.

As shown in FIGS. 1 and 2, the self-holding electromagnetically driven device in accordance with the invention comprises a pair of permanent magnets 1A and 18 in the form of disks which are facing each other in aligned relationship and .are spaced apart from each other. The permanent magnets 1A and IB have substantially the same diameter, and are disposed in opposed or bucking polarity relationship, as indicated by symbols N and S in FIG. 1. The permanent magnets 1A and 18 have electromagnetic coils 2A and 28 would respectively around the peripheries thereof in the same number of turns. The permanent magnets 1A and 1B are respectively provided with central apertures 6A and 6B, in which a control shaft or an operating rod 3 of metal is slidably mounted. Positioned between the permanent magnets and secured to the operating rod is an armature 4 of magnetic material in the form of a disk. Thus, the armature 4 can rest in either a first position, in which it is held fast to the magnet 1A by virtue of its magnetic force, or a second position, in which it is held fast to the magnet lB by virtue of the magnetic force of the latter. The operating rod 3 is provided at its lower end with a valve body 5 secured thereto. The valve body 5 is a part of valve means 7 comprising a valve housing 8 and a valve aperture 9. Feed pipes 10A and 10B are connected to opposite sides of the housing 8. The valve body 5 is adapted to open the aperture 9 so as to permit the passage of liquid through the valve means 7 when the armature 4 is held fast to the magnet 1A, and to close the aperture 9 so as to interrupt the liquid flow when the armature 4 is held fast to the magnet 1B. The electromagnetic coils 2A and 2B are connected respectively to a pair of alternating current power-supply means 11A and 118 through switching means 12A and 128, respectively, and through fullwave rectifier means 13A and 138, respectively.

Now, the operation of the device shown in FIG. I will be described.

It is supposed that initially the armature 4 is held fast to the magnet 1A as shown in FIG. 1 so that the valve aperture 9 is not closed by the valve body 5. When the switching means 128 is closed for an extremely short time, the coil 23 will be energized by the pulse of rectified current from the rectifying means 13B to reinforce the magnetic field of the magnet 18 so as to cause the armature 4 to be pulled toward the magnet 18 through the inherent magnetic force thereof plus the magnetic force of the coil 28 against the magnetic force of the magnet 1A, whereby the armature 4 will be lowered together with the operating rod 3 and the valve body 5, as a result of which the valve seat 5 will close the aperture 9 to stop the flow of liquid through the valve means 7. In this condition, however, even if the switching means 128 is opened to deenergize the coil 28, the armature 4 will remain held fast to the magnet 18 by virtue of the magnetic force of the magnet 18, thus assuringthat the valve aperture 9 is kept closed. Thereafter, if the other switching means 12A is closed for a short duration, the coil 2A will be energized to reinforce the magnetic field of the magnet 1A so as to cause the armature 4 to be pulled toward the magnet lA through the inherent magnetic force thereof plus the magnetic force of the coil 2A against the magnetic force of the magnet 18, so that the armature 4 will be raised together with the operating rod 3 and the valve body 5, as a result of which the valve body 5 will open the valve aperture 9 to recommence the flow of liquid from the pipe 10A to the pipe 108. In this condition, however, even if the switching means 12A is opened to deenergize the coil 2A, the armature 4 will remain held fast to the magnet 1A by virtue of the magnetic force thereof, thus assuring that the valve is kept open. The number of turns of each electromagnetic coil is selected so that it can produce a magnetic force large enough to attract the armature from the opposite pennanent magnet.

In FIG. I, the operating rod 3 is shown provided only at its lower end with a valve body 5. However, it should be understood that another valve body or any other operating member can be secured to the upper end of the operating rod so that two interrupter devices (valve, switch etc.) are controlled simultaneously.

In FIGS. 3 and 4 l have shown how the elements of the device of FIG. 1 are assembled in practice. The permanent magnets 1A and 18 having electromagnetic coils 2A and 2B wound respectively around them are inserted in a tubular casing 16 of nonmagnetic material with the armature 4 disposed between the magnets and with the operating rod 3 extended through the central apertures 6A and 6B in the magnets 4. The opposite ends of the casing 16 are closed by end plates A and 15B of magnetic material. EAch of the end plates has a cylindrical skirt which surrounds the associated coil, as shown in FIG. 4. Lead wires to the coils 2A and 2B are designated 14A and 148, respectively.

FIG. 5 shows a modified form of the device according to the invention which comprises substantially cylindrical coil-enveloping sleeve 17A and 17B of magnetic material in addition to the elements employed in the device of FIG. 4. Furthermore, in the device of FIG. 5, configurations of the armature and the end plates have been modified with respect to the corresponding elements of FIG. 4. The armature 4' employed in FIG. 5 is in the form of a cylinder having an annular projection or rib 4P midway along its axis. Each of the magnetically permeable sleeves 17A and 17B surrounds the associated coil and has an inwardly bent terminal portion or flange 17', 17" at its inner end. This bent portion of the sleeve permits the quick starting of the armature toward the associated permanent magnet upon the energization of the coil since a part of the lines of magnetic force generated by the energized coil pass through the gap between the central rib l8 and the corresponding flange 17' or 17" also functions as a stop for the armature. Thus, the structure of FIG. 5 may preferably be used where quick starting of the armature is required. It will be noted that the coils 2A and 28 extend axially toward each other, beyond the confronting ends (of like polarity) of the bar magnets IA and IE, to receive part of the central body of armature 4 in a corresponding armature position, this body being coextensive in cross section with the magnets so as to fit inside the coils as clearly shown in FIG. 5. It will also be seen that the intumed terminations 17, 17'' of sleeves 17A, 17B, projecting toward each other on opposite sides of rib 4P beyond the two coils, surround the central body with small annular clearance so that some of the flux passes directly into that body without traversing the rib 4?. As the spacing of the coils 2A, 2B exceeds the axial length of the armature body, the latter is never enveloped by both coils simultaneously.

In the devices of FIGS. 4 and 5, each of the end plates 15A and 15B is provided with an aperture to permit the operating rod to pass through. However, it is to be noted that either of the end plates can be deprived of its aperture so that one end of the casing is closed completely, by selecting the length of the operating rod appropriately.

In one embodiment of the invention which showed good result, the completed device was 36 mm. in diameter and 37 mm. in length, each permanent magnet was 15 mm. in diameter and 8 mm. in length and had a central aperture of 5 mm. in diameter, and each coil had 780 turns (AWG American Wire Gauge No. 30). A current of 0.65A was conducted for 20 milliseconds each time to shift the armature with certainty. The attraction force clue to excitation of the coil was 5 kg./cm. and the force required to pull away the armature from the permanent magnet was 3 kg./cm..

As seen from the foregoing, with the device according to this invention, it is suflicient for each operation of the device to supply energizing DC current to the selected one of the two electromagnetic coils for an extremely short time, and it is assured that the operating member. such as valve body 5, when displaced can be held fast in its alternate position by means of the magnetic force of the permanent magnet. without requiring any further application of electric power. Thus, the device according to this invention permits to minimize the electric power consumed and the heat generated during operation thereof. Furthermore, the device according to this invention is very simple in construction, inexpensive to manufacture, and reliable in operation under any operational condition.

Though this invention has been described in connection with the opening and closing of valve by way of an example, it is to be understood that its application is not restricted to such use. For example, it can be applied to electric apparatus, such as a refrigerator, washing machine, dishwasher, airconditioner, etc., as well as a magnetic switch, magnetic relay, magnetic valve, magnetic clutch, and other magnetic switching units. Furthermore, it is to be understood that many modifications and alterations can be attained without departing from the spirit of the invention. Besides, also with respect to the external power supply, many modification can be possible. For example, the AC power supply 11A, switching means 12A and full-wave rectifier means 13A may be replaced by a combination of a direct current power supply and an electric switch, or further it may be possible to replace the whole arrangement of the full-wave rectifier means 13A and 13B, switching means 12A and 12B, and AC power supply means 11A and 118 by a single DC power supply by employing a single-pole, doublethrow switch which is connected between the electromagnetic coils and the DC power supply and switched selectively between the coil 2A and the coil 2B.

I claim:

1. A bistable electromagnetic device comprising:

a pair of aligned permanent magnets with confronting ends of like polarity spaced apart along an axis;

a pair of electromagnetic coils respectively surrounding said magnets and centered on said axis;

an armature of magnetically penneable material axially movable between said confronting ends, said armature having a central body of a cross section substantially coextensive with that of said magnets provided with a peripheral rib in the midplane of said body projecting radially beyond said confronting ends, the spacing of said coils exceeding the axial length of said body;

a pair of magnetically permeable sleeves respectively surrounding said coils and extending therebeyond toward each other on opposite sides of said rib, said sleeves having confronting terminations constituting abutments for said rib in two alternate positions of said armature in which said body closely adjoins the corresponding magnets;

a pair of magnetically permeable end plates remote from said terminations forming part of a flux path from said magnets into said sleeves;

an operating element connected with said armature for displacement thereby; and

circuit means for the selective energization of either of said coils to reinforce temporarily the magnetic force of the respective magnet for attracting said armature toward same from a position adjacent the opposite magnet.

2. A device as defined in claim 1 wherein said terminations are intumed flanges surrounding said body with small clearance.

3. A device as defined in 'claim I wherein said coils extend 5. A device as defined in claim I wherein at least one of said toward each other beyond said magnets to receive part of said magnets and the adjoining end plate are provided with aligned body in corresponding positions f said a t re. axial bores, said operating element passing from said body 4. A device as defined in claim 1, further comprising a nonthrough Said boresmagnetic cylindrical housing embracing said sleeves. 5 

1. A bistable electromagnetic device comprising: a pair of aligned permanent magnets with confronting ends of like polarity spaced apart along an axis; a pair of electromagnetic coils respectively surrounding said magnets and centered on said axis; an armature of magnetically permeable material axially movable between said confronting ends, said armature having a central body of a cross section substantially coextensive with that of said magnets provided with a peripheral rib in the midplane of said body projecting radially beyond said confronting ends, the spacing of said coils exceeding the axial length of said body; a pair of magnetically permeable sleeves respectively surrounding said coils and extending therebeyond toward each other on opposite sides of said rib, said sleeves having confronting terminations constituting abutments for said rib in two alternate positions of said armature in which said body closely adjoins the corresponding magnets; a pair of magnetically permeable end plates remote from said terminations forming part of a flux path from said magnets into said sleeves; an operating element connected with said armature for displacement thereby; and circuit means for the selective energization of either of said coils to reinforce temporarily the magnetic force of the respective magnet for attracting said armature toward same from a position adjacent the opposite magnet.
 2. A device as defined in claim 1 wherein said terminations are inturned flanges surrounding said body with small clearance.
 3. A device as defined in claim 1 wherein said coils extend toward each other beyond said magnets to receive part of said body in corresponding positions of said armature.
 4. A device as defined in claim 1, further comprising a nonmagnetic cylindrical housing embracing said sleeves.
 5. A device as defined in claim 1 wherein at least one of said magnets and the adjoining end plate are provided with aligned axial bores, said operating element passing from said body through said bores. 